The F-22 raptor aircraft

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A US Air Force Stealth fighter F-22 Raptor takes off from Kadena Air Base on the southern Japanese island of Okinawa, Aug. 14, 2012. A group of F-22s arrived in Okinawa in late July, their first deployment overseas after the easing of flight restrictions imposed in mid-May because pilots reported dizziness and other symptoms of hypoxia. Greg Baker/AP

A pilot's outfit is displayed during a news conference at the Pentagon July 31, 2012, to provide an update on the Air Force Scientific Advisory Board's study into life support systems installed on the F-22. Manuel Balce Ceneta/AP

An F-22 fighter jet flies over Joint Base Elmendorf-Richardson in Anchorage, Alaska, Aug. 1, 2010, during the annual Arctic Thunder air show. A search is under way for an F-22 from the base that has been missing in the state’s interior. M. Scott Moon/Peninsula Clarion/AP

Vapor forms above the Raptor flown by a pilot of the Air Combat Command F-22 Demonstration Team at Joint Base Elmendorf-Richardson, Alaska, on July 26, 2012. Defense Secretary Leon Panetta approved a plan to lift flight restrictions following the ongoing correction of oxygen-deficit problems. Bill Roth/The Anchorage Daily News/AP